#include <vector>
#include <set>
#include <algorithm>
#include <iostream>

using namespace std;

class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        if (nums.size() == 0) {
            return false;
        }
        sort(nums.begin(), nums.end());
        for (int i = 0; i < nums.size()-1; i++) {
            if (nums[i] == nums[i+1]) {
                return true;
            }
        }
        return false;
    }
    
    bool containsDuplicateSet(vector<int>& nums) {
        return nums.size() > set<int>(nums.begin(),nums.end()).size();
    }
};
